Method for curing a lens-forming fluid

ABSTRACT

A method for curing a lens-forming fluid, including exposing the lens-forming fluid to an ultra-violet light, wherein the exposure time is between twenty seconds and thirty minutes, which can completely cure the fluid. The exposure can occur by placing the lens-forming fluid intermediate a plurality of ultraviolet light sources, in which the intensity of the ultra-violet light is at least 1.2×10 -2  watts per square centimeter at a wavelength of 350 nanometers. The lens-forming fluid preferably is a monomer. The prior art, in contrast, requires significantly longer exposure times to cure monomer or other lens-forming fluids.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention comprises an apparatus and method for lens castingand a gasket therefor. The present invention also encompasses a methodfor curing the casted lens and an apparatus and method for separatingthe cured lens from the molds used to form the lens.

2. Background Art

Glasses or spectacles must correspond to a person's prescription as wellas to the person's morphological and psychological characteristics. Theophthalmic lenses for glasses are made of a transparent material,usually glass or plastic, and are of a size and shape to produce desiredeffects, namely, focusing the light for the person's eye to see clearly.

The lenses use a well-defined geometrical configuration which determinesthe their optical properties. The shape of each lens is characterized bythree attributes: (1) the curvature of its two surfaces; (2) thethickness at its center and edges; and (3) its diameter. The twosurfaces of a lens can use various geometric configurations, includingthe following shapes: spherical; cylindrical; toric; piano; aspheric(usually elliptical); and progressive. For example, the surface of alens can have a constant radius along its different axes so that thesurface is symmetrical, which is known as a spherical surface. Thespherical lens surface mirrors the shape of a portion of a sphere inwhich all meridians have the same radius of curvature. The sphericalsurface may be either convex or concave.

Alternatively, the surface of the lens can have two axes, each having adifferent radius of curvature, so that the surface of the lens isasymmetrical. An astigmatic surface is an example of such anasymmetrical surface and is characterized by its two principal meridianshaving a different radius of curvature from each other. The meridianhaving the greatest radius of curvature is called the "axis," and theother meridian having the smaller radius is called the "perpendicularaxis." Astigmatic lens surfaces predominantly include a cylindricalsurface and a toric surface. A plano surface and aspheric surface areexamples of other lens surfaces used in the art.

For the cylindrical surface, the principal meridians along the axis hasan infinite radius of curvature, e.g., flat or straight, and theperpendicular axis has a radius of curvature which is the same as thecircular radius of a cylinder. Thus, a concave cylindrical surface isshaped to complementarily receive a cylinder on the surface and a convexsurface resembles the exterior surface of such a cylinder.

The toric surface resembles the lateral surface of a torus, e.g., shapedas the inner tube of a tire. Thus, a torus surface is similar to acylindrical surface, but the longitudinal axis curves instead of beingstraight as for a cylindrical surface. The perpendicular axis ormeridian on the toric surface has a radius of curvature smaller than theradius of the axis. As with a spherical and a cylindrical surface, atoric surfaces can be convex by having the shape of the exterior surfaceof a torus or, alternatively, may be concave by having the shape of theinner surface of a torus.

An astigmatic surface is used for a person with an ocular astigmatism,in which the cornea is elliptical instead of round. The orientation ofthe elongated portion of an astigmatic cornea varies from person toperson. For example, one person may have an axis at five degrees,another at thirty degrees, and another at yet a different orientation.The axis of the surface of the lens must be oriented to align with theorientation of the elongated portion of the cornea.

Different lens surfaces can be used in combination. Often, the frontsurface of a lens is spherical and the back surface is spherical,cylindrical, or toric. The front surface can alternatively be a planosurface. The optimum combination of surfaces in a lens is determined bythe optical properties, the proposed use, and the appearance of thelens.

In addition to shape, thickness is also an important characteristic of alens. The glass or plastic used to form the lens is a factor inestablishing the thickness. Many lens today are made from plasticbecause of its light weight, density, refractive index, and impactresistance. Examples of plastics used for lenses includemethyl-methacrylate (a thermoplastic resin, which is better known by itstrademark "Plexiglas"® or "Perspex"®) and dandiallyl glycol carbonate,which is also known as CR39.

CR39 is the most popular lens material used today, in part, because alllens types used in ophthalmic optics can be made from it. CR39 is apetroleum derivative of the polyester group, a family of polymerisablethermosetting resins. In production, a monomer is first obtained fromCR39. The monomer, which is a limpid liquid with the viscosity ofglycerine oil, remains in a liquid state in cold storage, but hardensafter several months at room temperature. To form a lens, the liquidmonomer is placed and contained in a volume defined by two molds and agasket. Once the monomer is in the volume, the monomer is cured to forma hardened polymeric lens taking the shape of the molds.

The glass molds used to form polymeric lenses are important in CR39 lensmanufacturing. Not only do the molds form the correct shape to the lensaccording to the optical characteristics required, but the surfacequalities of the finished lens depends on the accuracy of the moldssince the lens surfaces are a precise reproduction of the inner moldsurfaces. Accordingly, the mold surfaces are prepared with extremeprecision and, after manufacture, are heat toughened to withstand thestrain of the polymerization process.

An add power front mold, which forms a bifocal or trifocal portion tothe lens, can also be used in forming lenses. The add power moldincludes a segment curve, which is a concave depression cut into theconcave half of the mold, to form the add power segment on the frontsurface of the lens. This segment curve produces a convex surface forthe distance portion, together with a steeper convex surface for thereading add power segment.

The liquid monomer, as mentioned above, is placed into a volume definedby two molds and a gasket to form a lens. As shown in cross-section inFIG. 1, the prior art gaskets are known as T-gaskets G, which have abore B and two ends that each complementarily receives a respective moldM. Different T-gaskets G are required to form varying power lensesbecause each T-gasket G sets a predetermined axial separation betweenmolds M. That is, one T-gasket G sets the molds farther apart to form alens of a greater power compared with another T-gasket G used to form alower power lens. Accordingly, manufacturers must maintain separateT-gaskets for a +2 lens, another for a -3 lens, another for a -4 lens,etc.

One skilled in the art will also appreciate that forming an astigmaticsurface in a T-gasket G requires that the ends of the gasket have thesame shape as the inner surface of the mold M. For example, if the rearmold M forms a concave toric surface, then one end of the T-gasket Gmust have a complementary convex design to receive the mold M withoutleaking. And, different T-gaskets G must exist for each lens power usingthat mold shape.

Two manufacturing processes are used in making the lenses: directpolymerization and polymerization of a semi-finished lens. For thedirect polymerization process, the top mold is removed and a nozzledirected into the mold cavity to fill the volume with monomer. Theoperator then positions the top mold to be aligned with the T-gasket sothat excess monomer is squeezed out and air bubbles removed. The volumedefined by the two polished molds and the gasket forms the shape of thelens when cured. The drawbacks of this prior art system include thehandling, resulting mess, and wasted monomer. Also, some bubbles canstill remain in the volume, which can ruin the formed lens.Additionally, this process is labor intensive and, accordingly, oftenperformed in countries with an inexpensive labor pool.

To cure the monomer after the top mold is secured on the T-gasket, thefilled gasket assemblies are stored in racks and put into an oven forfourteen to sixteen hours to undergo a controlled temperature cycle thatprovides the correct degree of polymerization. After this lengthy curingprocess is completed, the gasket assembly is removed and the lens isremoved from between the molds. The lenses made using the directpolymerization process require a few finishing actions, such as edgetrimming, annealing to eliminate casting stress, visual checks toeliminate lenses which might have defects, and lens power checking witha focimeter. Once the lens is finished, it is packed for shipping to aretail vendor or mounted in glasses for a consumer.

The second process, polymerization of a semi-finished lens, produces alens known as a "semi." Unlike the direct polymerization lens, a semilens has a concave, unfinished side that is surfaced after the curingprocess is completed. Thus, instead of forming the lens to be mountedinto glasses with few finishing actions, the semi lens only has a singlefinished surface formed by a mold and the other surface is mechanicallyfinished after the lens has been cured. The semi lenses, accordingly,are made in stages, in which one surface is finished by a mold and theother surface is machine finished after curing. The surface of the lensformed by a mold is usually the front spherical surface, with or withoutadd power.

The unfinished side of a semi lens is usually surfaced using a speciallathe or generator in the same way as glass lenses, but other abrasivesare used. The polymeric lens is mounted on a circular holder and thesurface generated by a diamond grinding wheel. The curvatures arecontrolled by the relative positions and angles of the diamond wheel inrelation to the lens. This surface is then smoothed and finally polishedwith the appropriately-faced tool. Metal tools are used to smooth andpolish, each surface configuration having its own tool. A great numberof tools are, therefore, required to enable a complete range of lensesto be surfaced. Semi-finished lenses are generally put into stock andmachined when needed, e.g., a customer with a specific prescriptionorders the lens.

Semi lenses are used instead of by direct polymerization lens for verypowerful lenses, such as aphakic lenses or lenses with a very highcylindrical power. These powerful lenses cannot be made by directpolymerization because the difference in thickness between the centerand the edges of the lens create large stresses that can break the glassmolds with the T-gasket.

Another reason for making a semi lens is because of the numerous lensesrequired for different consumers, which is not conducive for massproduction. For example, a prescription may require a certain add poweron the front surface and an astigmatic back surface set at one of manydifferent orientations. That is, the add power portion must be orientedso that the flat top is horizontal, but the orientation of theastigmatic surface varies as the elongated portion of the cornea differsfrom person to person. As one skilled in the art appreciates, numerouspermutations exist for a specific add power and a given astigmatic backsurface at different orientations. Mass production of an infinitevariation of lenses is unfeasible and, accordingly, retail suppliersusually purchase a semi lens and machine the astigmatic surfaceimmediately before sale.

SUMMARY OF THE INVENTION

The present invention overcomes the disadvantages of the prior art andrevolutionizes the lens-forming process. Specifically, the presentinvention encompasses a gasket that can be used to form all powers andgeometric shapes of lenses, unlike the prior art T-gasket which islimited to forming one specific lens. The present invention alsoincludes an apparatus and method for forming lens using automationprocesses. Moreover, the present invention includes a method for curingthe formed lens in a fraction of the time as the prior art processesrequire. Furthermore, the present invention includes an apparatus andmethod for separating the cured lens from the molds used for forming andshaping the lens.

The gasket of the present invention is designed so that either or bothof the front mold and the rear mold are movably disposed within itsbore. At least one of the molds is axially movable within the borerelative to the other mold to a desired axial separation distancebetween the molds. Each of the different desired axial separationdistances corresponds to a separate lens power. The gasket of thepresent invention, unlike the T-gasket, also accepts various moldshaving different surfaces (i.e., spherical or astigmatic) to make thedesired lens surface. Since a single gasket is used to form multiplepowers of the lenses and different lens surfaces, the gasket of thepresent invention is referred to as a "universal gasket."

Additionally, as those skilled in the art are aware, the prior artT-gasket positions and holds the molds at a set separation, whichpresents a problem because the volume of monomer shrinks approximatelyten to fifteen percent when it is cured. Since the molds remainstationary using the T-gasket, this shrinkage creates internal stressesin the lens so that annealing is sometimes required. In contrast, thegasket of the present invention reduces stresses by allowing some axialmovement of the molds as the monomer volume shrinks during curing. Thus,annealing is usually not need for lenses made with the gasket of thepresent invention.

The casting method of the present invention encompasses positioning atleast one of the two molds both rotationally and axially relative to theother mold so that a lens of the correct thickness and power can beformed therebetween. That is, rather than relying on the gasket designfor setting the dimensions of the lens, the present invention usesautomation technology, including state-of-the-art motion control deviceshaving exacting tolerances, to position the molds within the gasket atthe appropriate axial separation distance from each other. The presentinvention also includes automated technology for rotating the moldsrelative to each other to the proper orientation, e.g. the toric backsurface mold is rotated to be properly aligned with the add power.

The desired lens is then formed by injecting the monomer into the volumedefined by the two molds and the bore of the gasket. The monomer isinjected by a needle instead of pouring the monomer into the gasket andspilling the excess off when the rear mold is positioned onto thegasket. The filling method used with the present invention significantlyreduces the quantity of monomer wasted and decreases the chances of airbubbles being formed into the lens.

Lens manufacturing is more economic and efficient using the presentinvention because the quantity of lens mold equipment necessary for lensmanufacturing is significantly reduced, as well as drasticallyreducing--if not eliminating--use of the hand-labor previously involvedin forming the lenses.

Furthermore, lenses produced using the present invention are improvedover the prior art. The quality of the machined finished surface of acut and polished lens from a semi is lower than that produced directlyby a glass mold. As one skilled in the art appreciates, craftsmen formthe front and rear glass molds by expending a tremendous number of hourscutting, grinding, and polishing the molds to make them as perfect aspossible, whereas often a lens surface cut by a generator may lack thisprecision.

The present invention, therefore, allows custom production of any axisorientation lens instantaneously using a single universal gasket designfor a particular prescription. Unlike the prior art systems, no furtherlens cutting or lens generation is required. That is, once a lens iscured using the present invention, it is a finished product, unlike thesemi-finished lens in the prior art. The present invention, accordingly,is quicker and cheaper than the prior art techniques.

The present invention also significantly reduces the time required tocure the monomer. As noted above, the prior art curing can take fourteenhours or more, depending on the lens design. The present invention has aone-step process, which is viable with use of the universal gasket ofthe present invention. In fact, lenses can be cured in about one minute.

Still another aspect of the present invention is a method and apparatusfor separating the cured lens from the molds, comprising directing afluid, such as carbon dioxide gas, at the interface of the lens and onemold. The gas, which is a temperature lower than the mold-lens-moldsandwich which has just been cured, causes the components to contract.The polymer forming the lens and the glass molds have differentcoefficients of thermal expansion causing a differential contractionrate. This differential contraction assists in breaking the bond betweenthe surface of the molds and the respective surface of the lens. Thisaspect of the present invention is an improvement over the prior arttechniques, which usually require physically pulling the componentsapart.

The present invention allows lenses to be made quickly to match thespecific prescription. The speed with which a lens can bemade--regardless of the lens power and surface shapes--is vastly reducedcompared with the prior art. For example, prior art systems allowmerchants to sell lens in about one hour, but only if the lens is astandard stocked lens. That is, one-hour service is not available if theprescription is for a toric lens with add power. In this situation, theprior art requires that the merchant use a semi with add power on thefront surface and cut the back surface of the lens into the desiredtoric prescription with a generator. As one skilled in the artappreciates, use of a generator is time intensive and, accordingly, anexception to the one-hour policy. The present invention, in comparison,allows the formation and curing of a lens in less than thirty minutes,which is faster than retailers produce a limited quantity of lenses anddays faster than the time to form other lenses from a semi.

The present invention, moreover, provides an opportunity for the doctorsto make the lenses which they prescribe in their offices--with only ashort waiting period for the patient. Given the speed that the presentinvention makes lenses and the short curing time, this option is prudentfrom a business standpoint by providing "one-stop" shopping for thepatient/customer. Thus, the patient can have an eye examination, waitabout thirty minutes and leave with glasses that were made to match theprescription from the examination.

BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a prior art T-gasket.

FIG. 2 is a cross-sectional view of a step gasket of the presentinvention.

FIG. 3 is a cross-sectional view of a straight-walled gasket of thepresent invention that shows ports in the gasket.

FIG. 4 is an exploded cross-sectional view of the molds and a gasket, inwhich the front mold defines an annular ring circumscribing its edge.

FIG. 5 is a perspective view of the present invention showing anassembly station, robotic arm, and filling stations.

FIG. 6 is a top plan view of the assembly station disposed outside thehood.

FIG. 7 is a side cross-sectional view of the assembly station with thepiston up.

FIG. 8 is a side cross-sectional view of FIG. 7, in which the piston isdown and also showing the camera.

FIG. 9 is a perspective view of a radial clamp used with the presentinvention.

FIG. 10 is a side view of a robotic arm used in conjunction with thepresent invention.

FIG. 11 is a top plan view of the system showing the robotic arm movedto one filling station and, in phantom, the robotic arm picking up thegasket and radial clamp from the assembly station and also moving toanother filling station.

FIG. 12 is a front view of the filling station.

FIG. 13 is a side cross-sectional view of the filling station takenalong line 13--13 in FIG. 12 when the lens-forming assembly firstarrives.

FIG. 14 is a side cross-sectional view of the filling station shown inFIG. 13 when the filling starts, in which the needles are inserted intothe gasket and the linear actuator has moved the rear mold to thecorrect axial separation distance from the front mold.

FIG. 15 is a simplified cross-sectional view partially in schematic of aUV curing device to cure the lens formed at the assembly and fillingstations.

FIG. 16 is a perspective of the separating device, partially inschematic, of the present invention used to separate the molds from thecured lens.

FIG. 17A is a cross-sectional view of the assembly fixture that showsthe gasket aligned to receive the rear mold into its bore.

FIG. 17B is a cross-sectional view of FIG. 17A, in which the rear moldis inserted into the gasket using the assembly station.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is more particularly described in the followingexamples that are intended as illustrative only since numerousmodifications and variations therein will be apparent to those skilledin the art. As used in the specification and in the claims, "a" can meanone or more, depending upon the context in which it is used. Thepreferred embodiment is now described with reference to the figures, inwhich like numbers indicate like parts throughout the figures.

OVERVIEW

Referring generally to FIGS. 2-17B, the present invention comprises amethod of lens casting and a gasket therefor. The present invention alsoencompasses a method for curing the casted lens and an apparatus andmethod for separating the cured lens from the components used forcasting the lens.

THE GASKET OF THE PRESENT INVENTION

The gasket 20 of the present invention can be used to form lenses ofvarying power, unlike prior art gaskets that require a different designfor each lens variant to be formed thereby. Referring to FIGS. 2 and 3,the gasket 20 of the present invention has a first end 22, an opposedsecond end 24, a body portion joining the first end 22 to the second end24, and a longitudinal, or axially, extending axis L. The gasket 20 hasan outer surface 26 and defines a bore 30 extending axially through thegasket 20 between its opposed ends 22, 24. The bore 30 forms an interiorsurface 32 that circumscribes the longitudinal axis L of the gasket 20.

The outer surface 26 of the gasket 20 is preferably circular or annular(as shown in perspective in FIG. 9), so that the preferred embodiment ofthe gasket 20 is essentially tubular. Although other shapes can be used(e.g., an elliptical cross-section, a polygonal cross-section, or othernon-circular shape), the circular cross-sectional embodiment ispreferred for its acceptance in the art, manufacturing considerations,and ease of automation.

The bore 30 of the gasket 20 receives both a front mold 40 and a rearmold 50 therein. As best shown in FIG. 4, the front mold 40 has aforward surface 42, an opposed back surface 44, and an edge 46circumscribing it. The edge 46 is of a size to be complementarilyreceived within at least a portion of the bore 30 so that the edge 46and the interior surface 32 of the gasket 20 form a substantiallyleak-proof seal therebetween.

The rear mold 50 likewise has a forward surface 52, an opposed backsurface 54, and a rim 56 circumscribing it. The rim 56 is sized to becomplementarily received within at least a portion of the bore 30 sothat the rim 56 and the interior surface 32 of the gasket 20 also form asubstantially leak-proof seal therebetween. Since the preferredembodiment of the gasket 20 is circular in cross-section as shown inFIG. 9, the molds 40, 50 preferably are also circular and have adiameter. When the front mold 40 and the rear mold 50 are both disposedwithin the bore 30 of the gasket 20 as shown in FIGS. 2 and 3, thecombination of components is called a lens-forming assembly 10, alens-forming structure, or a lens casting cell.

A volume is formed defined by the back surface 44 of the front mold 40,the forward surface 52 of the rear mold 50 and the interior surface 32of the gasket 20 when the molds 40, 50 are disposed within the gasket20. That is, the molds 40, 50 are placed in a spaced-apart relationshipwithin the bore 30 so that a volume is formed therebetween. This volume,referred to as the cavity 31, preferably has appropriate dimensions toform a desired lens when a lens-forming fluid is injected into thecavity 31 and cured therein. The cavity 31 is also shown in phantom inFIG. 4.

The lens-forming fluid is preferably a monomer. The preferred monomer ismanufactured by P.P.G. located at Monroeville, Ga., and sold under thetradename CR424. As one skilled in the art will appreciate, otherlens-forming fluids known in the art can be used with the presentinvention.

The present invention also includes a means for injecting the monomerinto the cavity 31. The preferred injecting means includes an injectionneedle, which is discussed in more detail below. The present inventionalso comprises a means for providing fluid communication between theouter surface 26 of the gasket 20 and the bore 30. The preferredproviding means includes a vent needle, which communicates with the bore30, thus allowing fluid communication between air in the cavity 31 andoutside the outer surface 26 to facilitate injecting the monomer andaxial movement of the molds 40, 50.

The front mold 40 or the rear mold 50 is axially movable within the bore30 relative to the other mold to a desired one of a plurality of axialseparation distances between the molds. The volume is different for eachaxial separation distance and, accordingly, the dimensions of the lensformed within the cavity 31 are also different for each axial separationdistance. As discussed in more detail below, the filling station of thepresent invention uses a computer subsystem (or a controller such as acomputer or microprocessor), robotic arm and linear actuators or servomotors to position the rear mold 50 exactly at a predetermined positionrelative to the front mold 40 in the bore 30. Since the automationincludes state-of-the-art motion control devices having exactingtolerances, the quality of the lens that the present invention producesis improved over prior art systems.

Referring to FIG. 2, the bore 30 of the gasket 20 forms a first diameteradjacent the first end 22 thereof that decreases along a portion of thelength of the bore 30. The first diameter is of a size tocomplementarily receive the edge 46 of the front mold 40. The bore 30also forms a constant second diameter adjacent the second end 24 of thegasket 20 that extends along a portion of the length of the bore 30, inwhich the second diameter is of a size to complementarily receive therim 56 of the rear mold 50.

A transition section 34 exists within the bore 30 between the firstdiameter and the second diameter. The transition section 34 comprises aninsert step 36, or ridge, for locating the front mold 40 at a fixed,known location within the bore 30. The transition step 36 is formed inthe interior surface 32 of the gasket 20 at the juncture of the firstdiameter and the second diameter. The front mold 40 is slidably receivedalong the interior surface 32 of the gasket 20 until it engages the step36 of the transition section 34. A portion of the back surface 44 of thefront mold 40 adjacent the edge 46 is shaped to complementarily engagethe transition section 34 to form a substantially leak-proof sealtherewith. That is, the transition section 34 has an angular geometryand the front mold 40 has a corresponding angular edge 46 thatcomplementarily mates with a portion of the transition section 34 toform a seal which substantially prevents leakage of the monomer disposedin the cavity 31. The angle of the transition section 34 can be a rightangle relative to the interior surface 32 to a twenty degree or moreoffset from the right angle orientation, preferably at a ten degreeoffset. The transition section 34 and the edge 46 of the front mold 40can alternatively have other mating shapes so that a leak-proof sealexists therebetween.

In this embodiment, the rear mold 50 is axially movable along at least aportion of the bore 30 for placement at the desired axial separationdistance from the front mold 40, which is stationarily disposed in thetransition section 34. Because the gasket 20 of the present invention isdesigned to be used with automation technology, the second diameter isconstant along the interior surface 32 of the bore 30 between thetransition section 34 and the second end 24 of the gasket 20. Thediameter of the rear mold 50 is substantially the same as the seconddiameter so that the rear mold 50 can be inserted into the bore 30 andaxially slid therealong to the desired axial separation distance fromthe front mold 40. As discussed above, when the front mold 40 and rearmold 50 are both disposed within the bore 30 of the gasket 20, thecavity 31 defined by the molds 40, 50 and the interior surface 32 of thegasket 20 can hold a fluid, such as the liquid monomer, without leaking.

In a variation of the gasket having the transition section which is notshown, the first diameter of the bore can remain constant from the firstend of the gasket moving inward and then abruptly expand to form anaxially-extending gap adjacent the transition section. The gap is of adimension to complementarily receive the edge of the front mold therein.This embodiment similarly locks the front mold into position adjacentthe transition section. That is, when the front mold is axially insertedinto the bore, it snaps into a position in the gap to be stationarilyand detachably maintained adjacent the transition section.

Another embodiment of the present invention shown in FIG. 3 comprises agasket 20 without a transition section or a step. Instead, the firstdiameter and the second diameter are the same so that the bore 30 has aconstant diameter along its entire length. Thus, similar to the slidablypositioning of the rear mold 50 in the transition section gasketembodiment, the front mold 40 and/or rear mold 50 are movably positionedwithin this straight-walled gasket. As one skilled in the art willappreciate, one mold can remain at a set position while the other moldis moved axially within the bore 30, similar to the transition sectionembodiment. Alternatively, both molds 40, 50 can be independently moved,either simultaneously or at different times, relative to each other. Thepreferred embodiment of the gasket 20 also has a key notch 28 adjacentits second end 24 to ensure the gasket 20 is correctly aligned in thelens forming process.

In comparing the transition section and straight-walled gasketembodiments, the disadvantage of the transition section gasket is that asmall amount of the liquid monomer can seep into and spread between thetransition section 34 and the front mold 40, although not substantiallyleaking past the front mold 40. Thus, the cured lens--when removed fromthe gasket 20--may not be "clean" along its outer periphery and thusrequires post-cure machining to remove the lens material that leakedinto the juncture of the front mold 40 and the transition section 34.Also, some monomer may be left in the bore 30 adjacent the transitionsection 34, which must be cleaned and removed before the gasket 20 canbe reused. Thus, additional time and expense may be required to reusethe transition section gasket embodiment because of machining the curedlens and/or cleaning the gasket 20 and front mold 40 for reuse. Anotherassociated drawback is that the number of uses, or life, of the gaskethaving the transition section 34 may potentially be shortened by thecleaning preformed thereon. The transition section gasket embodiment,however, is simpler to use in an automated system because the front mold40 is at a known position and the rear mold 50 is axially moved relativeto that fixed position to the desired axial separation distance.

Although the automation is more complicated for the straight-walledembodiment, using this gasket may nevertheless be less expensive in thelong term because of the substantial reduction of cleaning costs to thefront mold and gasket. Thus, the straight-walled embodiment may have alonger useful life.

Referring again to both FIGS. 2 and 3, each of the gaskets 20 of thepresent invention preferably further comprises at least one, andoptimally two, ports 38, 39 formed in the body portion of the gasket 20between its outer surface 26 and interior surface 32. The ports 38, 39are in fluid communication with the bore 30, specifically the cavity 31formed between the back surface 44 of the front mold 40, the forwardsurface 52 of the rear mold 50 and the interior surface 32 of the gasket20. Each port 38, 39 is adapted to receive a portion of a needle thereinso that the needle is in fluid communication with the cavity 31 withoutbeing inserted into the bore 30 itself. The injection needle is placedin fluid communication with one port (the injection port 38) and thevent needle is in fluid communication with the other port (the vent port39). That is, one port 38 is used to add monomer into the cavity 31 andthe other port 39 is used to vent air within the cavity 31 whendisplaced by the incoming monomer. The vent port 39 also provides fluidcommunication between outside the gasket 20 and the cavity 31 to allowair displaced by axially moving the molds 40, 50 relative to each otherto enter or exit the volume, depending on the relative axial motion ofthe molds 40, 50. Preferably, the needles penetrate the gasket 20 into arespective port 38, 39 in a direction substantially parallel to thelongitudinal axis L of the gasket 20, as opposed to at a steeper angle.This small angle or parallel alignment with the longitudinal axis Lminimizes the chances that the tip of the needle could contact one ofthe molds 40, 50. However, the steeper angle can be perpendicular to thelongitudinal axis L and the gasket 20 still function properly.

The ports 38, 39 are advantageous when the cavity 31 is relativelysmall, e.g., the back surface 44 of the front mold 40 is very close tothe forward surface 52 of the rear mold 50. In this situation, insertingthe tip of the needle into the bore 30 could contact one or both of thesurfaces 44, 52 of the two molds 40, 50. Such contact could potentiallydamage one surface of a mold or displace one mold so that the lens isnot the correct dimension or leakage occurs when the monomer is injectedinto the cavity.

It is also contemplated simply having a hole (not shown) through thegasket 20 to vent the air in the cavity. That is, the cavity 31communicates directly with the outside air instead of through the port39 and needle.

Another aspect of the gasket 20 of the present invention is the gasketmaterial. In the presently preferred embodiment, a desirablecharacteristic is that the gasket material is chemically compatible withthe lens-forming fluid to avoid inhibiting polymerization of the fluid.The gasket material should not include free-radical inhibitors, such as"UV" stabilizers and antioxidants. A UV stabilizer can leach into themonomer because the monomer acts almost like a solvent to draw such anadditive out of the gasket material and to mix locally into the monomer,causing the edges of the lens remain slightly wet after curing. Thewetness can be a problem because it potentially results in the monomeradhering to the gasket 20 and molds 40, 50, which requires cleaningbefore reuse and increases operating expenses. Accordingly a desiredgasket is a polymeric elastomer compatible with optical monomers whichwill not inhibit lens monomer during the curing process. Still anotheraspect of the gasket material is that it be relatively soft, for examplehaving a durometer between 40 and 70. Another concern is whether thegasket material has long-term stabilities.

In the presently preferred embodiment, a suitable gasket material isthermoplastic rubber that contains KRATON®G, astyrene-ethylene-propylene (butylene) block copolymer, sold by Shell OilCompany® of Houston, Tex. Such rubber includes those sold under thetrade names DYNAFLEX®G2703, 2711, and 2712 by GLS Corporation of Cary,Ill. These rubbers have a Shore A hardness ranging from about 43 to 62,a specific gravity of about 0.9 g/cc, a tensile modulus at 300%elongation ranging from about 355 to 470, tensile strength at break ofabout 680 to 1000 psi, and a tear strength of about 113 to 127. Anothercontemplated gasket material includes a PVC formulation. The gasketmaterial of the present invention, however, is not limited to a singlematerial. In fact, the desired gasket material can very depending on thespecific monomer compound used to form the lens. That is, a certaingasket material may be preferred with a particular lens-forming fluidand different type of gasket material with another lens material. Othercontemplated materials include elastomeric PVC, silicon, ethylene vinylacetate, or a mixture thereof.

The present invention also preferably includes a means for sealing thegasket 20 after the vent needle 232 or injection needle 252 has beenremoved from the gasket 20. Preferably, the sealing means comprises thegasket 20 being formed of PVC, silicon, KRATON®G, ethylene vinyl acetateor a mixture thereof. That is, the gasket material is self-sealing sothat the compound prevents leakage after the needles have been removed.

Other sealing means contemplated include, for example, the needle holebeing physically plugged when the needle is removed. Alternatively, thesealing means can comprise the needle remaining in the gasket to preventleakage of the fluid therefrom, but this embodiment is undesirablebecause of the handling limitations with a portion of the needleextending out of the gasket 20 and processing limitations withconstantly replacing the needle at the filling station. Still anotherembodiment of the sealing means is curing the monomer that leaks intothe needle hole by, for example, quickly exposing that monomer adjacentthe exit hold of the needle to UV light, heat, or other curing source.Instead of the monomer in the needle hole solidifying as the sealingmeans, heat applied to the gasket 20 itself can alternatively seal theneedle hole.

Referring again to FIG. 4, an alternative embodiment of the molds isshown. The front mold 40 has an annular ring 60 circumscribing the edge46 adjacent the back surface 44. The annular ring 60 increases the areain the cavity 31 adjacent the forward surface 52 of the rear mold 50,thus allowing better communication with the ports 38, 39 or with the tipof a needle if the needle is inserted substantially perpendicular to thelongitudinal axis L. The resulting bulge in the formed lens will beremoved during processing after curing is completed. As one skilled inthe art will appreciate, an annular ring can alternatively oradditionally be included on the forward surface 52 of the rear mold 50.

THE METHOD AND APPARATUS OF LENS CASTING

As an overview, the lens-forming assembly 10 is first processed at anassembly station 110 and then at a filling station 200, which are showngenerally in FIG. 5 and collectively referenced as 100. A frame 104supports the stations 110, 200. In the preferred embodiment, the molds40, 50 are rotationally aligned relative to each other and placed withinthe bore 30 of the gasket 20 at the assembly station 110. At the fillingstation 200, the molds 40, 50 are axially moved within the bore 30 to bespaced apart from each other the desired axial separation distance(e.g., the appropriate separation to produce a lens of a desiredthickness). The lens-forming fluid is also injected at the fillingstation 200 into the cavity 31 formed between the two molds 40, 50 andthe bore 30. The method of the present invention is discussed based onusing the transition section gasket embodiment, as opposed to thestraight-walled gasket.

A. The Assembly Station

Referring now to FIGS. 5-8, the assembly station 110 comprises a meansfor supporting the gasket 20 so that the molds 40, 50 are insertableinto the bore 30. The assembly station 110 preferably has threepositioning collets: a front mold positioning collet 120, a rearmold/gasket positioning collet 130, and a clamp positioning collet 150.The collets are arranged on a plate 112 which slides along rails 114. Adrive cylinder 116, such as a pneumatic or an electric cylinder, movesthe sliding plate 112 along the rails 114 between a loading position andan assembly position. In the loading position, which is shown in FIG. 6,the sliding plate 112 is disposed outside the periphery of a hood 102and, in the assembly position shown in FIG. 5, the plate 112 is withinthe periphery of the hood 102.

The hood 102, which is preferably formed of glass or see-throughplastic, acts as a barrier and covers the filling station 200 and arobotic arm 160 (which is discussed below) to ensure that the operatoris protected from interfering with the components. The hood 102 is alsoused for safety considerations, such as to protect the operator frombeing inadvertently contacted by the robotic arm.

In the preferred embodiment, the front molds 40 are stored at onestorage station (not shown) located near the assembly station 110. Thegaskets 20 are stored at another location, which is also positioned nearthe assembly station 110, or at the same storage station as the frontmolds 40. The gaskets 20 preferably each have one rear mold 50 disposedin their respective bores 30. As discussed in more detail below, therear molds 50 are preferably placed in the bore 30 of a respectivegasket 20 after completion of the curing process and after the curedlens is separated from the two molds 40, 50. As one skilled in the artwill appreciate, the gasket 20 and molds 40, 50 can be stored indifferent combinations, e.g., the molds 40, 50 and gaskets 20 all storedas separate components, the front mold 40 disposed in the gasket 20 andthe rear mold 50 stored separately, or both molds 40, 50 disposed andstored within the bore 30 of the gasket 20.

To start the process in the preferred embodiment, the operator entersthe parameters of the lens to be formed (e.g., the prescriptionincluding add power) into the computer subsystem (not shown), such as bya keyboard. The computer subsystem also includes a memory subsystem anda hard disk to run computer programs. The power means (not shown) usedto power electrical components in the present invention, such as thecomputer subsystem, is preferably a 120V AC power source.

Algorithms used in a computer program determines the appropriate frontand rear molds 40, 50 to be used to form the desired lens and thecomputer subsystem then provides an output indicating the correct moldsto use. The front mold 40 is usually spherical and the rear mold 50 isspherical or astigmatic, e.g., toric or cylindrical. The front mold 40can also be adapted to form bifocals or trifocals for the add power.

In one embodiment of the present invention, the computer subsystemdisplays on its monitor the output indicating the appropriate molds touse. Another embodiment additionally illuminates a light (not shown) atthe storage stations above the specific location where the appropriatemolds are stored. The indicating lights assist the operator in locatingthe appropriate molds to reduce the chance of the operator inadvertentlypicking an incorrect mold to make the lens.

One means for transferring the components of the lens-forming structure10 to the sliding plate 112 of the assembly station 110 is the operatorphysically moving the components. The present invention can also use anautomated means (not shown) for moving the components of thelens-forming structure 10 to the plate 112 of the assembly station 110.In the automated system, the computer subsystem directs anelectronically-controlled arm (not shown) to transfer the appropriatemolds 40, 50 and one gasket 20 to the plate 112 of the assembly station110. Once the molds 40, 50 and gasket 20 are transferred to the plate112, then the plate 112 slides along the rails 114 to the assemblyposition within the periphery of the hood 102 from the load position.

The front mold positioning collet 120 of the assembly station 110 has anupstanding circular lip 122 adapted to receive one front mold 40. Otherfront mold supporting means include a vacuum support (not shown), springclips (not shown), and the like. The front mold positioning collet 120can have a light (not shown) to indicate that a front mold is disposedon the collet or an interlock to block the process from continuing untila front mold is positioned on the collet 120.

The rotational orientation of a spherical front mold 40 does not presentan issue when placing it on the front mold positioning collet 120.However, orientation is important for a front mold adapted to form anadd power lens or an asymmetrical mold. In the preferred embodiment, thefront mold positioning collet 120 is marked with a series of parallelmarking lines (not shown). The operator aligns the line forming the topportion of the flat top so that it is aligned with or parallel to themarking lines. Thus, a front mold having add power can be placed at oneof two positions, which are offset 180° from each other and bothparallel to the marking lines. For progressive add power front molds inwhich no discernable markings exist on the front mold or asymmetricalfront molds, the mold can be etched or scribed with a line to use foralignment. An electronic eye (not shown) or the like can be used toverify proper positioning before allowing the process to continue.Alternatively, the automated embodiment using an imaging system canproperly orient the front mold on the front mold positioning collet 120.

One reason for properly orienting the add power is so that its flat topportion is oriented vertically during filling the cavity 31 with thelens-forming fluid to prevent air bubbles from being trapped. Bubblesare more likely to remain in the cavity 31 if, for example, the flat topis horizontally oriented during filling. Additionally, it is importantthat the front mold 40 be properly positioned relative to an astigmaticrear mold 50 to ensure that the add power is correctly oriented on theformed lens.

The front mold positioning collet 120 preferably also has a plurality ofair holes 124 or recessed vents that direct ionized air from an ionizedair supply (not shown) toward the back surface 44 of the front mold 40.The ionized air ensures that dust and other impurities are removedbefore the front mold 40 is placed into the bore 30 of the gasket 20,which occurs as discussed below.

The rear mold/gasket positioning collet 130 has a gasket support lip 132adapted to support the second end 24 of the gasket 20 thereon, which isthe end of the gasket 20 closest to the rear mold 50 disposed within thebore 30. As with the front mold 40, the operator, or alternatively anautomated system, places the gasket 20 with the rear mold 50 therein onthe collet 130. Other means (not shown) for supporting the gasket 20 andrear mold 50 include separate collets for each component, vacuumcollets, grippers, or the like.

As discussed above, the rear mold 50 is preferably placed into the bore30 of the gasket 20 before placing the rear mold 50 at the storagestation. It is important to have the rear mold 50 at a predeterminedorientation within the bore 30 of the gasket 20. The front and rearmolds 40, 50 do not initially need to be in a correct relativeorientation to each other, but instead at known positions from which onemold can later be rotated to align correctly with the other mold.

The rotational position of the gasket 20 when placed at the assemblystation 110 is important so that the rear mold 50 will be at a knownrotational orientation on the rear mold/gasket positioning collet 130.Also, the position of the gasket 20 is important because it may haveports 38, 39 formed therein into which the injection needle and ventneedle are inserted. Accordingly, as shown in FIGS. 2 and 3, thepreferred embodiment of the gasket 20 has a key notch 28 adjacent itssecond end 24 or other means to ensure the gasket 20 is correctlyaligned on the support lip 132. In one embodiment, if the key notch 28of the gasket 20 is not properly aligned, then an interlock means (notshown) blocks the lens forming process from continuing. For example, thesliding plate 112 will not move from the load position to the assemblyposition until the interlock means is satisfied by the gasket 20 beingproperly positioned on the rear mold/gasket positioning collet 130. Theinterlock means can also provide a visual indication, such as warninglight at the assembly station 110 or a message on the monitor of thecomputer subsystem.

The assembly station 110 also comprises a means for inserting the frontmold 40 into the bore 30 of the gasket 20, which preferably is a movablearm. Other contemplated embodiments of the front mold inserting means(not shown) include the operator manually moving and inserting the frontmold 40 and use of slides, pneumatics, linear motors, gantry robots, andthe like.

The movable arm used in the preferred embodiment picks up the front mold40 disposed on the front mold positioning collet 120 and axially pushesthe front mold 40 into the bore 30 of the gasket 20 through its firstend 22 until the back surface 54 of the front mold 40 contacts theinsert step 36 of the transition section 34. As discussed above in thegasket description, the transition section 34 is used for positioningthe front mold 40 at a fixed, known location and forms a substantiallyleak-proof seal between the front mold 40 and the step 36. Once thefront mold 40 is properly positioned within the bore 30 of the gasket20, the movable arm disengages from the inserted mold and is moved to anout-of-the-way position or, alternatively, remains engaged to the frontmold 40 to support the gasket 20 on the rear mold/gasket positioningcollet 130.

In the preferred embodiment, the movable arm is a robotic arm 160 shownin FIGS. 5 and 10 having a pneumatic gripper 162 that detachably engagesthe forward surface 42 of the front mold 40. An example of the roboticarm 160 is commercially available from Mitsubishi® Electronic under thetradename "Movemaster RV-M2." The computer subsystem directs andcontrols operation of the robotic arm 160. The robotic arm 160 may alsoinclude an internal computer that interfaces with the computer subsystemto control movements of the robotic arm 160.

As best shown in FIG. 10, the body of the robotic arm 160 is disposedwithin the periphery of the hood 102. A shoulder 164 connects the bodyof the robotic arm 160 to its upper arm, which is connected by an elbow166 to the forearm 167. The pneumatic gripper 162 is connected to theforearm 167 of the robotic arm 160 at a wrist 168. The robotic arm 160has a full range of motion due to horizontal rotation at the pivot atthe base and vertical lift by movement of the shoulder 164, elbow 166,and the wrist 168 of the robot. A wrist tool plate 169, located betweenand connected to the pneumatic gripper 162 and wrist 168 of the robot,provides full rotational movement for the pneumatic gripper 162. Therobotic arm 160 offers five degrees of freedom, not including the hand,and a large position memory and is driven by DC servo motors (not shown)and contains internally-routed pneumatic lines (not shown).

A contemplated embodiment of the present invention entails the roboticarm 160 orienting the front mold 40 to a desired orientation when movingthe front mold 40 into the bore 30 of the gasket 20, regardless of itsinitial orientation when placed on the front mold positioning collet120. That is, the robotic arm 160 twists the front mold 40 as necessaryto position it properly within the bore 30 at a predeterminedorientation relative to the gasket 20. The front mold 40, however, wouldneed to be marked by a means detectable by the robotic arm 160 so thatthe robotic arm 160 has a reference point.

The assembly station 110 also preferably includes a means for insertingthe rear mold 50 into the bore 30 of the gasket 20. The rear moldinserting means, which is a part of the rear mold/gasket positioningcollet 130, also preferably further comprises a means for removing therear mold 50 from the bore 30 of the gasket 20. Thus, the rear moldinserting means can both insert the rear mold 50 into the bore 30 andremove the rear mold 50 from within the bore 30.

The rear mold inserting means preferably comprises a movable piston 134adapted to detachably engage a portion of the rear mold 50, e.g., itsback surface 54, and remove the rear mold 50 from the bore 30 of thegasket 20 or insert the rear mold 50 therein. More specifically, therear mold inserting means comprises a mold support plate 136 adapted todetachably engage the back surface 54 of the rear mold 50 and a means,connected to the mold support plate 136, for moving the mold supportplate. The movable mold support plate 136 for the rear mold 50 iscircumscribed by the support lip 132 of the rear mold/gasket positioningcollet 130.

The mold support plate 136 is movable between an insert position shownin FIG. 7, in which the mold support plate 136 is substantially at thesame height as the support lip 132, and a retracted position. In theretracted position shown in FIG. 8, the mold support plate 136 is moved,or retracted, into a support frame 138, which comprises a plurality ofupstanding support rods 139 extending between the support lip 132 and acylinder mounting plate 140. The mold support plate 136 is disposedadjacent the cylinder mounting plate 140 when fully in the retractedposition. A portion of a "T"-shaped piston 134, which moves within acylinder 142, is fixedly attached to the mold support plate 136.Although other driving means (such as an electrical solenoid) can beused, the "T"-shaped piston 134 is preferably pneumatically controlledand moves in response to a positive air pressure applied to a cylinder142 through an appropriate air port. That is, the piston 134 is movedupwardly within the cylinder 142 in response to pressurized air appliedthrough a first port 144 and downwardly in response to pressurized airapplied through a second port 146. The mold support plate 136correspondingly moves with the attached piston 134.

When the rear mold 50 and gasket 20 are loaded onto the rear mold/gasketpositioning collet 130, the rear mold 50 is adjacent the mold supportplate 136. A plurality of vacuum ports 148, which are connected to avacuum source (not shown), are located in the mold support plate 136.When the mold support plate 136 is at the insert position, the vacuumports 148 communicate with and create a suction force on the backsurface 54 of the rear mold 50 by activation of the vacuum source. Thesuction force is sufficient to pull and separate the rear mold 50 fromwithin the bore 30 when the mold support plate 136 is moved toward theretracted position. That is, the rear mold 50 is pulled out of the bore30 by activation of a vacuum source and concurrent movement of the rearmold support plate 136 to the retracted position. The rear mold 50 isretracted from the gasket 20 in the preferred embodiment approximatelythe same time as the robotic arm 160 is moving the front mold 40 fromthe front mold positioning collet 120 and inserting it through the firstend 22 of the gasket 20.

The present invention also comprises a means for rotating the gasketsupport means relative to the longitudinal axis L of the gasket 20. Anastigmatic mold surface has different radii in different axes. As oneskilled in the art will appreciate, the orientation of the rear mold 50relative to the front mold 40 is critical, particularly for a front molddesigned to form a multi-focal lens having add power. Thus, adjustmentof the rotational position of the rear mold 50 relative to the frontmold 40 may be required, which can occur when the rear mold 50 is in theretracted position using a rotating means.

The rotating means encompasses the computer subsystem directing one ofthe support lip 132 or the mold support plate 136 to rotate or twist thegasket 20 or the rear mold 50, respectively, a desired number ofdegrees, if necessary. Pressurized air then moves the piston 134 and themold support plate 136 back to the insert position so that the rear mold50 is reinserted into the bore 30 of the gasket 20 at the orientation towhich it has rotated. Thus, the rear mold 50 will be at a desiredrotational orientation relative to the front mold 40 when reinserted,which provides the proper orientation of an astigmatic rear mold 50relative to the front mold 40. It is presently preferred to rotate thesupport lip 132 and connected gasket 20 and front mold 40 instead ofrotating the mold support plate 136 holding the rear mold 50.

The present invention also preferably further comprises a means fordetermining a selected dimension of the rear mold 50, specifically theheight of the rear mold 50. The preferred embodiment of the presentinvention operates on the premise that the dimensions of the front moldare held within specified tolerances, which is fairly accurate becauseof the grinding techniques used to form the front mold. However, such apremise is less accurate for the rear mold 50, particularly for itscenter thickness, or height when the mold is horizontally disposed. Thatis, the height from the back surface 54 of the rear mold 50 to the topof the forward surface 52 of the rear mold 50 used to make the same typeof lens can be slightly different among the different rear molds. Thetolerances among rear molds is the biggest variable in forming the lensand, in fact, can be greater than five hundredths (0.05) of amillimeter, which is the minimum tolerance needed to ensure the desiredaccuracy to form the lens in the preferred embodiment. Thus, the presentinvention uses a determining means.

To determine the height of the rear mold 50, the determining means inone embodiment comprises a means for optically receiving an image of atleast a portion of the profile of the rear mold 50 when in the retractedposition, a means for digitizing the image of the rear mold 50, and ameans for creating information from the digitized image of the rear mold50, such as information about the height or thickness of the rear mold50. The creating means generates a signal that is communicated to thecomputer subsystem and stored in its memory subsystem.

A camera 149, the preferred optically receiving means, is positioned toview the rear mold 50 when the mold support plate 136 is moved to theretracted position. The CCD or similar camera 149 records the image ofthe rear mold 50, which the digitizing means and creating means use todetermine the height of the rear mold 50. The camera 149 can also usegain control, an automatic iris, and the like to ensure that the imageof the rear mold 50 is received properly.

The digitizing means can be a frame grabber (not shown), which is alsoknown as a capture board. Other contemplated embodiments of thedigitizing means are a digital camera to replace the analog camera andframe grabber, a scanable linear sensor, and the like. The creatingmeans and the digitizing means can be integral as the same component.

In still another embodiment, the molds 40, 50 can be premeasured andmarked with a bar code that represents the measurements. The operatorscans the bar code, which signals the computer subsystem with thedimensions of the rear mold 50 before placing the rear mold 50 onto therear mold/gasket positioning collet 130. The bar code can be placed inink on one mold face (e.g., the forward surface 52 of the rear mold 50)so that the bar code image transfers onto the cured lens, which assistsin tracking the lens. The bar code would then be replaced on the moldface before being used to make another lens. The bar code transferred tothe lens would be positioned at a location that would be cut away whenused in glasses. Also, the back surface 54 of the rear mold 50 itselfcan be etched with an indication that corresponds to the information inthe bar code to be reprinted onto the forward surface 52.

Since in this embodiment the computer subsystem does not know in advancewhich of a plurality of rear molds 50 is used for a given lens power,the computer subsystem would be required to store and use an enormouslookup table incorporating the different characteristics of everyspecific mold. If the system uses, for example, a thousand molds, it maybe simpler to view each rear mold 50 with the camera 149 or acquire theinformation from a bar code. Thus, the height of the rear mold 50 isascertained in this embodiment for the respective rear mold 50 and theascertained height is used later to calculate the desired axialseparation distance between molds 40, 50 to obtain a lens having thecorrect thickness. That is, the ascertained height of the rear mold 50is used to calculate the distance that the molds 40, 50 are axiallymoved within the bore 30 of the gasket 20.

Continuing with the assembly process, the rear mold 50 is reinserted tobe disposed adjacent the second end 24 of gasket 20, as opposed to beinginserted to a calculated desired axial separation distance. Venting thecavity 31, which is the volume formed by the two molds 40, 50 and bore30, is not necessary because of the short distance that the rear mold 50is inserted into the bore 30. As described in more detail below, thefilling station 200 preferably includes a means for axially moving therear mold 50 within the bore 30 to the desired axial separation distancefrom the front mold 40. Thus, the axial separation distance between thefront and rear molds 40, 50 is not important at the assembly station110.

In one alternative embodiment, however, it is contemplated to insert therear mold 50 into the bore 30 to the desired axial separation distancefrom the front mold 40 using the rear mold inserting means. Although notrequired, using a needle or other means to vent the cavity 31 during theadjustment in this alternative embodiment would be desirable to ensurethat the molds 40, 50 are not misaligned relative to the interiorsurface 32 of the bore 30 when moving toward each other.

The last collet of the assembly station 110 is the clamp positioningcollet 150. A means for securing the molds 40, 50 within the bore 30 isstored on the clamp positioning collet 150. The clamp positioning collet150 has a circular indention therein sized to receive the gasket 20. Thesecuring means for the lens-forming assembly 10 can, optionally, beadded at this location. The securing means can be used to hold each moldstationary relative to each other within the bore 30 of the gasket 20.Thus, after the molds 40, 50 are axially moved to be separated from eachother the desired distance at the filling station 200, the securingmeans firmly holds the molds 40, 50 so that their relative positions donot change. Accordingly, the securing means in the preferred embodimentis disposed around the outer surface 26 of the gasket 20 at the clamppositioning collet 150 and fully tightened at the filling station 200.

Referring to FIG. 9, the preferred embodiment of the securing means is aradial clamp 152 that maintains the position of the molds 40, 50 bycircumscribing and tightening about the outer surface 26 of the gasket20. The preferred radial clamp 152 has a belt portion 156 and a cam lock158 used to tighten the belt. The tightened belt presses the bodyportion of the gasket 20 inwardly to ensure that the molds 40, 50 do notchange their relative position and to enhance the seals that the gasket20 forms with the molds 40, 50. However, the frictional force of thegasket 20 with the molds 40, 50 does not preclude a mold (e.g., the rearmold 50 in the step gasket embodiment) from sliding toward the othermold as the monomer contracts during curing. Another advantage of theradial clamp 152 is that it can also provide a handle member 154, suchas the cam or other protrusion, for the robotic arm 160 or operator tograsp when handling the lens-forming assembly 10.

When aligning the components at the assembly station 110, the roboticarm 160 moves the gasket 20 with the two molds 40, 50 in its bore 30from the rear mold/gasket positioning collet 130 to the clamppositioning collet 150. The robotic arm 160 also twists the gasket 20,if necessary, before inserting the lens-forming assembly 10 into theradial clamp 152 at the clamp positioning collet 150. If, for example,the gasket 20 is twisted when the rear mold 50 is in the retractedposition, then the robotic arm 160 rotates the gasket 20 while moving itto the clamp positioning collet 150 so that the gasket 20 is in thepredetermined orientation. This rotation occurs so that the ports 38, 39of the gasket 20 are at the correct location for inserting the injectionneedle 252 and vent needle 232 at the filling station 200 and the flattop will be oriented substantially upright when positioned at thefilling station 200 to prevent catching bubbles. If the flat top is notproperly oriented, it has a tendency to trap air bubbles along its edgebecause of the high-energy area existing from the surface tension at itsedge.

Also, the radial clamp 152 can include a plurality of apertures (notshown) therethrough, in which one aperture aligns with a respective port38, 39 of the gasket 20. The injection needle 252 is inserted throughone aperture and the vent needle 232 is inserted through the otheraperture so that both needles 232, 252 communicate with respective ports38, 39 of the gasket 20.

An alternative embodiment of the present invention does not use asecuring means. The gasket, however, should be thicker and the moldsshould fit tighter within the gasket to ensure no leakage occurs. Thisalternative embodiment is presently less desirable based on theautomated process used.

B. The Filling Station

After assembling the gasket 20, molds 40, 50, and the radial clamp 152at the assembly station 110, the robotic arm 160 transfers the formedlens assembly to the filling station 200, which is shown in FIG. 11. Therobotic arm 160 operating at the assembly station 110 is shown inphantom. Also the robotic arm moving to another filling station 200 isalso shown in phantom.

Now referring to FIGS. 12-14, the filling station 200 preferablycomprises a means for supporting the lens-forming structure 10 and ameans for axially moving the rear mold 50 relative to the front mold 40to a desired one of a plurality of axial separation distances betweenthe molds 40, 50 (e.g., the rear mold 50 is moved in the step gasketembodiment). The front mold 40 could alternatively be moved if thestraight-walled gasket was used instead of the step gasket.

The filling station 200 has an upright support plate 210 supporting atop bracket 212 and a bottom bracket 214. The top bracket 212 supportsthe vent assembly 230 and the bottom bracket 214 supports the fillassembly 250.

The axial moving means preferably comprises a cylindrical piston 220having an end adapted to engage the mold to be slid within the bore 30.A linear actuator 222, or servo motor, which generates an output, isdisposed on the base of the frame and includes a ball screw (not shown)upon which a slide (not shown) traverses or rides. A means formechanically coupling the linear actuator 222 to the piston 220,specifically a coupler 224, translates the output of the linear actuator222 into movement of the piston 220. The piston 220 axially moves therear mold 50 disposed within the bore 30 of the gasket 20 relative tothe front mold 40. FIG. 13 shows the rear mold 50 before it is pushedalong the bore 30 of the gasket 20 and FIG. 14 shows the cylindricalpiston 220 having pushed the rear mold 50 toward the front mold 40 sothat the desired separation distance exists therebetween and the cavity31 is the desired dimension. Electric or pneumatic power is used tooperate the linear actuator 222.

In one embodiment, the piston 220 pushes the rear mold 50 further intothe bore 30 toward the front mold 40, as opposed to pulling the rearmold 50. That is, the separation between the front mold 40 and rear mold50 when assembled at the assembly station 110 is such that pushing isthe only action that the piston 220 performs on the rear mold 50 to formthe lens. However, a vacuum line (not shown), which is connected to avacuum source (not shown), can extend through the piston 220 so that avacuum or suction can be exerted on the back surface 54 of the rear mold50 to push or pull the rear mold 50. The vacuum line can also ensurethat the piston 220 securely engages the rear mold 50 as the piston 220pushes the rear mold 50 so that the mold does not tilt, which wouldcause the lens to be improperly formed or the injected monomer to leakpast the rear mold 50.

The filling station 200 also comprises a means for providing fluidcommunication between the bore 30 intermediate the front and rear molds40, 50, or the cavity 31, and outside the outer surface 26 of the gasket20. Additionally, the filling station 200 comprises a means forinjecting a desired amount of a lens-forming fluid into the cavity 31.The providing means is also known as the vent assembly 230 and theinjecting means is known as the fill assembly 250. The vent assembly 230and fill assembly 250 are structurally and operationally similar.

The vent assembly 230 comprises a vent needle 232 that has a base end234 and a tip end 236, which is adapted to penetrate through a portionof the gasket 20. The tip end 236 of the vent needle 232 is in fluidcommunication with the base end 234 to allow a fluid, such as air, toflow therebetween.

The vent assembly 230 also comprises a means for shifting the ventneedle 232 between a first position and a second position. In the firstposition shown in FIG. 14, the tip end 236 of the vent needle 232 is influid communication with the cavity 31 and, in the second position shownin FIG. 13, the tip end 236 is spaced apart from the gasket 20 and itsbore 30. The shifting means preferably is a pneumatic cylinder 240 thatdrives a syringe piston 244, which is in contact with a coupler block246. A syringe support block 242 holds the vent needle 232 and isfixedly attached to the coupler block 246. Thus, the syringe supportblock 242 and vent needle 232 move in response to the syringe piston244. A protective cover (not shown) optionally shields the tip of thevent needle 232 when the vent needle 232 is in the second position.

The injection means, or fill assembly 250, includes an injection needle252 having a insertion end 254 that penetrates through a portion of thegasket 20 to be in fluid communication with the cavity 31, a receivingend 256 adapted to be in fluid communication with a supply of thelens-forming fluid, and a passage (not shown) extending therebetween.The passage allows the lens-forming fluid to traverse from the receivingend 256, through the passage, out of the insertion end 254 and into thecavity 31.

The fill assembly also includes a means for conveying the injectionneedle 252 between an insert position shown in FIG. 14, in which theinsertion end 254 of the injection needle 252 is in fluid communicationwith the cavity 31, and a withdrawn position. In the withdrawn positionshown in FIG. 13, the insertion end 254 is spaced apart from the gasket20. The conveying means of the fill assembly, similar to the ventassembly 230, includes a pneumatic cylinder 260, a syringe piston 262, acoupler block 264, and a syringe support block 266. The injection needle252 is connected to a fill conduit (not shown) in fluid communicationwith a fill line. A protective cover (not shown) also optionally shieldsthe tip of the injection needle 252 when in the withdrawn position.

The robotic arm 160, as discussed above, moves the lens-formingstructure 10 to the filling station 200 and positions it on thesupporting means of the filling station 200. The vent needle 232 ismoved to the first position, in which the needle 232 is inserted intothe gasket 20 to communicate with the cavity 31 via one port 39 of thegasket 20. The vent needle 232 thus allows air to escape from the cavity31 so that when one mold is slid relative to the other mold by thepiston 220 of the axial moving means, atmospheric pressure existstherebetween.

The computer subsystem marks in its coordinate system where the frontmold 40 is located, which is adjacent the step 36 in the gasket 20. Thecylindrical piston 220, which is attached to the linear actuator 222,slides the rear mold 50 to obtain the correct thickness of the desiredlens to be formed. As discussed above, the computer subsystem hasascertained the actual height of the rear mold 50 from the imagerecorded by the camera 149 at the assembly station 110, from bar codedata, or from other means. Thus, the computer subsystem directs the rearmold 50 to be pushed toward the front mold 40 a predetermined distanceto form a lens having the desired thickness, in which the computersubsystem uses the height of the specific rear mold 50 ascertainedearlier in the process. If desired for increased precision, the computersubsystem can adjust the axial separation distance to account forshrinkage (approximately ten to fifteen percent by volume) that willoccur when the monomer is cured. After axially moving the rear mold 50,the front and rear molds 40, 50 are at the correct rotationalorientation relative to each other and are separated from each other atthe desired axial distance.

The next step in the process is injecting the lens-forming fluid,namely, the liquid monomer, into the cavity 31. The vent needle 232already communicates with the cavity 31, preferably at its highestpoint, and the injection needle 252 is inserted into the other ports 38to be in communication with the cavity 31. The monomer is then suppliedthrough the injection needle 252 into the cavity 31. The presentinvention allows effective venting and filling of the cavity 31,regardless of the separation of the front and the rear molds 40, 50 andthe quantity of monomer to be injected.

As shown in FIGS. 13 and 14, the gasket 20 is positioned with theinjection port 38 disposed below the vent port 39 so that any airbubbles that may form as the monomer is injected into the cavity 31 areeffectively displaced and vented. However, the fill or injection rateused is slow enough so that no bubbles form.

The filling station 200 includes a means for detecting a level of themonomer added by the injecting means. The detecting means preferablycomprises a means, in fluid communication with the vent needle 232, forcreating a sub-atmospheric pressure in either locally in the tip end 236of the needle 232 or in the cavity 31 and a means, also in fluidcommunication with the vent needle 232, for sensing pressure in thevolume. The vent needle 232 is connected to a vacuum source (not shown)by a first line 248 that draws air through a vent in the needle 232about one-half an inch from the tip end 236, thereby lowering thepressure in the tip end 236 or the cavity 31 to a pressure less thanatmospheric, e.g., pulling a slight vacuum. For ease of illustration,the first line 248 is shown closer to the base end 234 of the needle 232than in the preferred design. A second line (not shown), which sensesthe vacuum, is connected to a vacuum sensor (not shown).

When the liquid monomer fills the cavity 31 and reaches the vent needle232, which is located at the highest position in the cavity 31, thevacuum sensor detects the pressure increase, e.g., the vacuum lowers,which triggers the computer subsystem to turn off the monomer fill. Asone skilled in the art will appreciate, the quantity of monomer wastedis a few micrograms, e.g., that amount required to fill the smallportion of the needle 232. In comparison, the monomer wasted in theprior art systems is orders of magnitude larger.

The vacuum used can be slightly below atmospheric pressure. A lowerpressure is not necessary since the primary purpose of that vacuum is tofunction as the fill sensor, not to assist in the filling. That is, ifthe vacuum exists in the cavity 31 that may be beneficial during fillingby further reducing the chance of forming bubbles, the advantages arenot significant compared to venting the cavity 31 to atmosphere.

As one skilled in the art will appreciate, other sensors can be used todetect when the gasket 20 is filled with monomer, such as an electroniceye (not shown), other optic sensors (not shown), and the like.

An alternative method of performing the filling process is for thecomputer subsystem to calculate the volume of monomer to inject into thecavity 31 and stop filling the cavity 31 once the calculated volume hasbeen added. Accordingly, the use of sensors in this alternative fillingmethod is optional. It is also contemplated that the predeterminedamount of monomer to be injected before the molds 40, 50 are axiallymoved toward each other so that the cavity 31 will be completely filledwhen the molds 40, 50 are at the desired axial separation distance.

The location at which the vent and injection needles 232, 252 enters thegasket 20 can vary. In the preferred embodiment, the needles 232, 252move axially through a portion of the gasket 20 until the respective tipis in fluid communication with a port 38, 39. The port is also in fluidcommunication with the cavity 31. This design is preferred to analternative embodiment in which the respective needles 232, 252 traversethrough the gasket 20 perpendicular to the outer surface 26 so that thetip of the needle physically enters into the cavity 31. Inserting aportion of either the vent needle 232 or the injection needle 252 cancause problems in this alternative embodiment if the front mold 40 andrear mold 50 are axially separated by a small distance when forming alow-power lens. Also, a mold having the annular ring 60 shown in FIG. 4can be used for a small separation distance.

After completing the filling, the needles 232, 252 are then retractedand the gasket 20 is sealed by the sealing means, preferably by thematerial of the gasket self-sealing. The radial clamp 152 of thesecuring means can then be tightened, securing the molds 40, 50 in thebore 30 at the desired distance from each other. As one skilled in theart will appreciate, the radial clamp 152 could alternatively betightened after the axial moving means positions the rear mold 50 at thecorrect location relative to the front mold 40 and before the monomer isinjected.

The present invention can use multiple filling stations 200 and assemblystations 110. For example, one embodiment uses two assembly stations andtwo filling stations operating simultaneously. A single robotic armassembles one lens-forming assembly while another lens-forming assemblyis injected with monomer at the filling station. The robotic arm thentransfers the newly assembled lens-forming structure to the otherfilling station for filling, removes the lens-forming assembly intowhich monomer was injected, and then assembles the next lens-formingassembly. The process would continue to repeat. Another contemplatedembodiment has four stations and two robotic arms, in which one roboticarm is used for assembling and loading lens-forming assemblies onto thefilling stations and another for unloading the filling stations. As oneskilled in the art will appreciate, other variations in the number ofrobotic arms and filling stations can be used.

THE CURING METHOD

The robotic arm 160 removes the lens-forming assembly 10 injected withmonomer from the filling station 200 and delivers it to the operator oranother automated system for curing the monomer. The curing method ofthe present invention involves exposing the monomer to an ultraviolet("UV") light for a desired time, which is significantly less than theprior art. The UV light exposure is the only step in the preferredembodiment. Alternatively, after exposing the monomer to UV light, themonomer is then heated for a predetermined time, such as in an infra-red("IR") oven. The second, heating step solidifies the monomer to form thehardened polymeric lens if not sufficiently cured in the UV step.

The desired exposure time to the UV light is between twenty (20) secondsand thirty (30) minutes, more preferably between thirty (30) seconds andtwo (2) minutes, and most preferably between forty-five (45) seconds andone and a half (11/2) minutes. The exposing step occurs by placing themonomer between a plurality of UV light sources, preferably one adjacentto each end of the gasket 20 so that the UV light passes through theglass molds to the monomer into the cavity 31. The intensity of the UVlight sources 312 is preferably about 1.2-1.3×10⁻² watts per squarecentimeter at a wavelength of 350 nanometers.

The process of exposing the lens-forming assembly 10 can be automatedby, for example, using the curing station 300 in FIG. 15. The operatorconnects the handle member 154 of the clamp 152 to a movable cylinderrod 310, which moves the clamp 152 and lens-forming assembly 10upwardly. At the top position, the two molds 40, 50 are each exposed toa UV light source 312 so that the UV light passes therethrough tointeract with the monomer. The computer subsystem or other automated ormanual means energizes the UV light sources 312 for a desired period,after which time the movable cylinder rod 310 lowers so that theoperator can remove the clamp 152 and lens-forming assembly 10.

The curing method of the present invention is quicker, less complex, andmore efficient than the prior art processes because at the unique gasketdesign. The curing method completely cures the monomer and reduces thestresses in the cured monomer so that the cured lens is stronger than alens cured using prior art processes. Stresses are also reduced becausethe rear mold 50 slides along the bore 30 of the gasket 20 when themonomer volume shrinks by approximately ten to fifteen percent whencured. The molds in the prior art T-gasket, in contrast, remainstationary, regardless of the stresses from shrinkage.

THE SEPARATING APPARATUS AND METHOD

After the liquid monomer has been cured, the solidified lens must beseparated from the gasket 20 and molds 40, 50. Since the gasket 20 isflexible, the two molds 40, 50 and the lens sandwiched therebetween caneasily be slid out of the gasket 20 after the radial clamp 152 isremoved. However, separating the molds 40, 50 from the lens is moredifficult because a strong bond is created by the surface tensionbetween the lens and contacting mold surfaces. The present invention,thus, also includes an apparatus and method for separating the molds 40,50 from the newly formed lens.

Referring now to FIG. 16, the separating device 400 of the presentinvention comprises a means for supporting the lens and molds and ameans for directing a fluid onto a portion of at least one of the lensor mold. As one skilled in the art will appreciate, the lens and moldhave a different coefficient of thermal expansion because they areformed of different materials. The fluid, preferably a gas, has atemperature which is lower than the temperature of both the mold and thelens, which have recently been removed from the heat source, i.e., theUV light or the IR oven. The temperature of the gas is usually less thanambient temperature and the temperature of the lens and mold is greaterthan ambient.

Examples of gases that can be used include pressurized air, oxygen,nitrogen, and, most preferably, carbon dioxide ("CO₂ "). The gas,directed by the directing means, cools the warmer mold-lens-moldsandwich 410 causing the glass molds and cured monomer to contract.Since the coefficients of thermal expansion are different for the glassand polymer lens being cooled, a differential shrinkage rate exists forthe two materials. This different contraction rate assists in breakingthe surface bond between the molds 40, 50 and the respective surfaces ofthe lens. As one skilled in the art will appreciate, the greater thetemperature differential between the gas and the mold-lens-mold sandwich410, the more rapid the cooling and the more effectively the lens isseparated from the molds 40, 50.

The directing means comprises a nozzle 412 connected to a supply 418 ofthe gas at a pressure greater than atmospheric pressure. The nozzle 412has an inlet 414 in fluid communication with the supply 418 of the gasand an outlet 416 that directs the gas toward the lens and the mold,specifically at the interface of the lens and one mold. As an example,each nozzle 412 can have an internal diameter of approximately three (3)millimeters that reduces to approximately three tenths (0.3) of amillimeter at the outlet 416. Such a nozzle 412 allows the fluid exitingtherefrom to increase to a high velocity. The directing meansencompasses one nozzle 412, more preferably two nozzles, and mostpreferably four nozzles which are each disposed approximately every 90°around the edges of the mold-lens-mold sandwich 410. FIG. 16 shows anembodiment with four nozzles 412.

The supporting means comprises a horizontally disposed member 420 havingan upper surface 422 adapted to support the lens and mold thereon and anopposite lower surface 424. The preferred supporting means also has anaxis of rotation R. The present invention further comprises a means formoving a selected one of the supporting means or the nozzles 412 of thedirecting means relative to the other. As one skilled in the art willappreciate, the nozzles 412 can rotate relative to the mold-lens-moldsandwich 410, the nozzles 412 and the sandwich 410 can rotate oppositedirections, or both the nozzles 412 and the sandwich 410 can rotate thesame direction at different speeds so that relative motion existstherebetween. It is also contemplated that no relative motion existsbetween the directing means and the supporting means.

In the preferred embodiment, however, the supporting means rotates aboutits axis of rotation R while the nozzles 412 remain stationary so thatthe mold-lens-mold sandwich 410 spins relative to the nozzles 412. Themeans for rotating the member 420 preferably comprises a motor 430generating a rotational output and a segment 432 having opposed ends.One end of the segment 432 is connected to the motor 430 and the otherend of the segment is connected to a portion of the lower surface 424 ofthe member 420 so that the output of the motor 430 rotates the member420 about its axis of rotation R. The motor 430 can be powered byelectricity, pressurized air, or other means known in the art.

Still referring to FIG. 16, the outlet 416 of each nozzle 412 ispreferably disposed at a different height relative to the other nozzles412 because at least one outlet 416 of one nozzle 412 should be directedat the interface of the lens and an adjacent mold, regardless of thethickness of the lens. That is, each nozzle 412 directs the gas to adifferent height on the edges of the mold-lens-mold sandwich 410 to coolthe materials. The rotating means, in conjunction, creates relativespinning motion between the mold-lens-mold sandwich 410 and the nozzles412. Directing the gas at the interface of the lens and the mold isassisted since the gas expands and spreads out after leaving the outlet416 of the nozzle 412 to cover a vertical height of approximately onemillimeter or more, depending factors such as gas velocity, nozzledesign, and the separation distance between the outlet 416 of the nozzle412 and the mold-lens-mold sandwich 410.

When high-velocity carbon dioxide, the preferred gas, is directed fromthe nozzle 412 at the interface of the lens and one of the molds 40, 50,some of the gas molecules reach the interface therebetween. It isbelieved that some of the carbon dioxide turns into "dry ice" whenreaching the lens-mold-lens sandwich 410 and expands after penetrating aspace existing between the lens and one mold. The expansion forces theadjacent lens and mold away from each other, assisting in breaking theproximity contact of the components. The penetrating carbon dioxideadditionally cools the lens and mold at their interface to acceleratethe differential shrinkage therebetween. And, the more separation thatoccurs, the deeper the carbon dioxide can penetrate to continue theexpansion and the cooling. This apparatus and method of the presentinvention can cause the mold and lens to separate without any externalphysical or mechanical shear stresses placed on the components.

The present invention, however, can also comprises a means forphysically bending a portion of a selected one of the lens or the mold.The preferred bending means comprises at least two engaging members (notshown), each engaging member having a contacting surface adapted todetachably engage a separate portion of the lens, and a means for movingthe engaging members relative to each other so that the respectivecontacting surfaces cause the lens to bend. The contacting surface canbe formed as dull teeth, a knurled surface, or other pattern thatprevents slippage between the engaging member and the edge of the lens.

The moving means comprises at least one actuator which generates anoutput, a means for mechanically coupling each linear actuator to onerespective engaging member, and a means for energizing the actuator. Theoutput of the actuator translates into movement of the coupled engagingmember. Thus, the contacting surface of the engaging member squeezesinwardly against the plastic of the lens to deform it away from theglass mold, thereby causing slight physical deformation to break thesurface tension bond therebetween. The opposed edge of the lens can beplaced against either a stationary engaging member or another engagingmember coupled to a separate actuator, in which the two actuators movetheir respective engaging members toward each other. It is less desiredto deform physically the lens as compared to using the cool gas toseparate the components.

Still another means to separate the lens from the mold is the operatorsubmerging the components into soapy water. This alternative allowssimultaneously cleaning and separating the lens and molds.

After the molds 40, 50 have been separated from the cured lens, themolds 40, 50 and gasket 20 can be reused or discarded. If the componentsare to be reused, the operator places the rear mold 50 into the bore 30of the gasket 20 at a predetermined rotational orientation relative tothe gasket 20. The operator can use an assembly fixture 500, which isshown in FIGS. 17A and 17B, to aid in inserting the rear mold 50 intothe bore 30 and to reduce the physically handling of the rear mold 50.

The gasket 20 can be used again to make another lens if it is in anacceptable condition. However, the life of the gasket 20 is much shorterthan that of the glass molds. If the gasket 20 requires extensivecleaning or has been damaged, the gasket 20 is discarded and laterground to be recycled.

The assembly fixture 500 has a center portion 510 adapted to supporthorizontally the back side of the rear mold 50. Surrounding the centerportion 510 of the assembly fixture 500 is a spring-loaded receiver 512adapted to engage the second end 24 of the gasket 20. Thus, the centerportion 510 holds the rear mold 50 and the gasket 20 is pusheddownwardly against the spring-loaded receiver 512 so that the rear mold50 is accepted into the bore 30 of the gasket 20.

The rear mold 50 is marked, for example, by a line etched on the surfacethat does not contact the monomer when forming the lens, e.g., the backsurface 54. The operator aligns the rear mold 50 at a desired rotationalorientation relative to the aligning apparatus. The rotationalorientation of a toric back lens relative to the gasket 20 must be at aknown position for orienting at the assembly station 110. The operatorthen positions the gasket 20 above the assembly fixture 500 androtationally orients a marking on the gasket 20 to be in registry withthe etched line on the rear mold 50. In the preferred embodiment, thegasket 20 will only be accepted by the assembly fixture 500 when thegasket 20 is at a desired rotational orientation, thus helping to ensurethat the gasket 20 and the rear mold 50 are at the desired rotationalorientation relative to each other. The key notch 28 can be used toensure that the gasket 20 is properly aligned with the spring loadedreceiver 512. FIG. 17A shows the components properly aligned.

FIG. 17B shows that the operator has pushed the gasket 20 downwardly onthe assembly fixture 500 so that the rear mold 50 is received within aportion of the bore 30. When the operator starts to push downwardly, thegasket 20 moves against the spring force and receives the rear mold 50into its bore 30. When the rear mold 50 is axially received apredetermined distance within the bore 30, movement of the gasket 20 isstopped by the receiver 512, which cannot be compressed further. Therear mold 50, accordingly, is placed into the bore 30 at a desireddistance.

Although the axial position of the rear mold 50 within the bore 30 isnot critical, the assembly device nevertheless ensures that the rearmold 50 is consistently positioned the same distance each time, insteadof the variations occurring among different operators. This improves theoperation of the present invention by, for example, ensuring that therear mold 50 is not inserted too far within the bore 30 to hinderoperation of the mold support plate 136 moving the rear mold 50 to theretracted position at the assembly station 110. As one skilled in theart will appreciate, this process can be automated so that a robotic armor the like performs the process of placing the rear mold 50 in the bore30 of the gasket 20 at a known rotational orientation.

From a handling perspective, it is also easier to store the rear mold 50in the gasket 20. Since the surface 44, 52 of the mold used to form thelens is an active surface, contaminants, such as those on a person'sfingers, can ruin it. But touching the other surface 42, 54 of the mold40, 50, which is not used to form the shape of the lens, is not aproblem. For the rear mold 50, the forward surface 52, which is orientedto face the interior of the gasket 20, is the active surface and theback surface 54, which is handled, does not present a problem. It iseasier to place the rear mold 50 in the bore 30 so that the active sideis protected by the gasket 20 and handle the front mold 40 by theforward surface 42, e.g., the robotic arm 160 contacts the forwardsurface 52.

The front mold 40 and the gasket/rear mold 20, 50 then are moved to theappropriate storage area near the assembly station 110 to formadditional lenses. The operator, for example, places the components on amoving belt. The front mold 40, which can be stored in a carrier, isplaced on one belt and the gasket/rear mold 20, 50 on another belt.Sensors detect that the molds reached the end of the belt and, ifnecessary, stop the movement of the respective belt. Another operator atthe end of the belt then places the components at the correct storagelocation so that the process of the present invention can be repeated.

Although the present invention has been described with reference tospecific details of certain embodiments thereof, it is not intended thatsuch details should be regarded as limitations upon the scope of theinvention except as and to the extent that they are included in theaccompanying claims.

What is claimed is:
 1. A method for curing a lens-forming fluid,comprising the steps of:a. placing the lens-forming fluid in a moldingcavity from a supply of the lens-forming fluid, the molding cavity beingdefined by a front mold, a rear mold and a gasket, wherein the gaskethas a first end and a second end, a body portion joining the first endand the second end and having an outer surface, a bore extending axiallythrough the body portion for receiving the front mold and the rear mold,the bore having a longitudinal axis, and at least one port formedintermediate the outer surface of the body portion and the bore, theport being separated from the ambient air by the outer surface of thebody portion and being in fluid communication with the molding cavity,and wherein the lens-forming fluid from the supply of the lens-formingfluid is placed into the molding cavity through the port; b. terminatingfluid communication between the supply of the lens-forming fluid and theport; and c. exposing the lens-forming fluid to an ultra-violet lightfor a desired time, thereby curing the lens-forming fluid.
 2. The methodof claim 1, wherein the desired exposure time is between thirty secondsand two minutes.
 3. The method of claim 1, wherein the desired exposuretime is between forty-five seconds and ninety seconds.
 4. The method ofclaim 1, wherein the desired exposure time is between twenty seconds andthirty minutes.
 5. The method of claim 1, wherein the lens-forming fluidis a monomer.
 6. The method of claim 1, wherein the exposing step occursby placing the lens-forming fluid intermediate a plurality ofultraviolet light sources.
 7. The method of claim 1, wherein theintensity of the ultra-violet light is at least 1.2×10⁻² watts persquare centimeter at a wavelength of 350 nanometers.
 8. A method forcuring a lens-forming fluid placed, comprising the steps of:a. placingthe lens-forming fluid in a molding cavity from a supply of thelens-forming fluid, the molding cavity being defined by a front mold, arear mold and a gasket, wherein the gasket has a first end and a secondend, a body portion joining the first end and the second end and havingan outer surface, a bore extending axially through the body portion forreceiving the front mold and the rear mold, the bore having alongitudinal axis, and at least one port formed intermediate the outersurface of the body portion and the bore, the port being separated fromthe ambient air by the outer surface of the body portion and being influid communication with the molding cavity, and wherein thelens-forming fluid from the supply of the lens-forming fluid is placedinto the molding cavity through the port; b. exposing the lens-formingfluid to an ultra-violet light to cure the lens-forming fluid, whereinthe exposure time is between twenty seconds and thirty minutes; and c.subsequent to the exposing step, heating the cured lens-forming fluid tofurther solidify the cured lens-forming fluid.
 9. The method of claim 8,wherein the desired exposure time is between thirty seconds and twominutes.
 10. The method of claim 8, wherein the desired exposure time isbetween forty-five seconds and ninety seconds.
 11. The method of claim8, wherein the heat in the solidifying step is generated by infra-redheat generator.
 12. The method of claim 8, wherein the lens-formingfluid is a monomer.
 13. The method of claim 8, wherein the increasingstep occurs by placing the lens-forming fluid intermediate a pluralityof ultraviolet light sources.
 14. The method of claim 8, wherein theintensity of the ultra-violet light is at least 1.2×10⁻² watts persquare centimeter at a wavelength of 350 nanometers.